idle problem going into reverse

[Jxw]

i have a vr v6 driveline, runs perfectly normal and everything seems to work great.

the problem i have noticed is when i go from park or neutral while idling to reverse it almost stalls the engine when it engages, with the pc hooked up and monitoring it there seems to be quite a delay till it raises the idle speed to the desired rpm for being in gear, seems to just up the iac steps due to the rpm dropping long before the desired idle setting changes

Not to much of a hassle just one of those characteristic glitches some cars have

From park to OD/D/2/1 it's almost instant to upping the rpm to the set idle rpm, works fine if i go from p/n to OD then to reverse(even if i do it as quick as i can) Tried 2 different pcm's and a few different memcal tunes (bmza, bply, blcb) looked through the tunes with tunerpro but i can't see anything specific to reverse.....

Tried holding the shifter with button depressed so it's only just in the rev position from p and n so it doesn't seem to be the position.....

I'm leaning towards the trans pressure sensor on it's way out for the R sensor, but from reading the manual and the valid combinations if this was true it should've shown an error 28 as the combination would be invalid...

Also checked the p/n switch it's fine.
PWR/Eco selected no difference.

any suggestions?

[08sky_way]

You could try cleaning the throttle body and IAC valve. That sorted mine out when I had a similar problem.

[Chappo_1]

You could try cleaning the throttle body and IAC valve. That sorted mine out when I had a similar problem.

Same here. Stalling going into reverse from park, then stalled going from reverse to drive. Cleaned a ton of crud out of the throttle body passages. Fixed it up.

[Jxw]

that was all cleaned when the engine was in bits being rebuild, iac was taken out and all the carbon cleaned off it and the tb and all slightly oiled before it went back together.....

engine was completely dismantled and has new bearings and gasket kit put through it, bores deglazed, all clearances checked to be within factory tolerance, bout the only thing different to factory is after market timing chain set with the cam advanced 4°, P/N to drive fine, P?N to OD/D then R fine..... only P/N to R
If the ac/c is on and the engine is idling higher from that it's also fine... this one has me buggered and i'm sure there's a fix for it. just a matter of working it out.

[wildeagle44]

I've got this problem as well, My throttle body is all clean but what/where is the iac?

[Jxw]

here's a spare one i prepared earlier, the black thing with the arrow pointing to it, held in by 2 torx T20 screws, idle air control
also there's a hole inside the tb that you can see on the same side (this is not the one off my car it's a random spare)

[RX25SE]

Vs use IAC and ignition timing to control idle.

Make sure the DFI has a good earth (clean and has zinc oxide grease) to the alloy bracket and the bracket is well earthed to the head (scrape the paint off).

Mine would almost stall between drive and reverse with a clean throttle body and IAC; and this fixed it.

Remember to reset the ECU when you're done.

[Jxw]

dfi module/coil packs changed and earth points good, no change and tried a couple of ecus and diff tunes as mentioned above..
thought the bugger had sorted itself out but once to normal operating temp 90deg+ and it's at its lowest idle rpm it's still doing it, if i override the desired idle rpm higher it stops doing it.
Taught it a lesson and programmed a higher desired idle for p/n closer to drive rpm which also stepped up 15 rpm, still notice the problem but at least it's not dropping to 400-500 rpm and almost stopping now. will worry about finding the issue when what ever is causing it breaks completely if it ever does. without pulling the trans out, changing the fluid pressure switch assembly and stripping it down making sure there's no blockages i've checked everything else i can think of.